/*
 *  Copyright 2014 The WebRTC Project Authors. All rights reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

// Borrowed from Chromium's src/base/numerics/safe_conversions.h.

#ifndef RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
#define RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_

#include <limits>

#include "rtc_base/checks.h"
#include "rtc_base/numerics/safe_conversions_impl.h"

namespace rtc {

// Convenience function that returns true if the supplied value is in range
// for the destination type.
    template<typename Dst, typename Src>
    inline constexpr bool IsValueInRangeForNumericType(Src value) {
        return internal::RangeCheck<Dst>(value) == internal::TYPE_VALID;
    }

// checked_cast<> and dchecked_cast<> are analogous to static_cast<> for
// numeric types, except that they [D]CHECK that the specified numeric
// conversion will not overflow or underflow. NaN source will always trigger
// the [D]CHECK.
    template<typename Dst, typename Src>
    inline constexpr Dst checked_cast(Src value) {
        RTC_CHECK(IsValueInRangeForNumericType<Dst>(value));
        return static_cast<Dst>(value);
    }

    template<typename Dst, typename Src>
    inline constexpr Dst dchecked_cast(Src value) {
        RTC_DCHECK(IsValueInRangeForNumericType<Dst>(value));
        return static_cast<Dst>(value);
    }

// saturated_cast<> is analogous to static_cast<> for numeric types, except
// that the specified numeric conversion will saturate rather than overflow or
// underflow. NaN assignment to an integral will trigger a RTC_CHECK condition.
    template<typename Dst, typename Src>
    inline Dst saturated_cast(Src value) {
        // Optimization for floating point values, which already saturate.
        if (std::numeric_limits<Dst>::is_iec559)
            return static_cast<Dst>(value);

        switch (internal::RangeCheck<Dst>(value)) {
            case internal::TYPE_VALID:
                return static_cast<Dst>(value);

            case internal::TYPE_UNDERFLOW:
                return std::numeric_limits<Dst>::min();

            case internal::TYPE_OVERFLOW:
                return std::numeric_limits<Dst>::max();

                // Should fail only on attempting to assign NaN to a saturated integer.
            case internal::TYPE_INVALID:
                FATAL();
                return std::numeric_limits<Dst>::max();
        }

        FATAL();
        return static_cast<Dst>(value);
    }

}  // namespace rtc

#endif  // RTC_BASE_NUMERICS_SAFE_CONVERSIONS_H_
